The corrosion of metals occurs in many forms when metals react with their environments. There are many devices for measuring some types of corrosion for predicting or preventing the failure of a selected component. However, one form of corrosion for which there is no known monitoring device is SCC. Stress corrosion cracking refers to intergranular or intragranular cracking caused by the simultaneous presence of tensile stress and a specific corrosive medium. A specific chemical environment must exist in which a susceptible material has a tensile stress applied to it in order for this type of corrosion to occur. Under these conditions, a material that is otherwise corrosion resistant, will fail in a brittle fashion. For example, stainless steel will fracture in a short amount of time if a sufficient tensile stress is applied to it while it is exposed to a hot concentrated chloride environment. Stress corrosion cracking is described in Mars G. Fontana, CORROSION ENGINEERING, Third Edition, McGraw-Hill, New York, 1986, pp. 109-142.
Although there are no known devices made for monitoring SCC, an existing device made for measuring electrochemical noise (indicating pitting corrosion) has been suggested as capable of measuring SCC. This device includes a pair of electrodes spaced a small distance apart in a chemical environment. When pitting occurs, the voltage measured between the electrodes changes slightly, yet abruptly. This voltage change qualitatively represents the occurrence of pitting. It has been claimed that this device could work for monitoring SCC, but this claim has not been proved and is viewed with some doubt.
Therefore, the need exists for a device for monitoring the SCC of a selected material exposed to a specific chemical environment.